Tell Capybara that #captcha_string is hidden
Tell Capybara that #captcha_string is hidden

Using ``visible: false`` in our capybara finder lets us get around the "you can't interact with hidden elements" opinions that Capybara has, and this means we can now still use the hidden field in the captcha to fill in the value properly.

unboxed/e-petitions,alphagov/e-petitions,telekomatrix/e-petitions,StatesOfJersey/e-petitions,ansonK/e-petitions,unboxed/e-petitions,telekomatrix/e-petitions,unboxed/e-petitions,oskarpearson/e-petitions,alphagov/e-petitions,unboxed/e-petitions,joelanman/e-petitions,alphagov/e-petitions,telekomatrix/e-petitions,joelanman/e-petitions,StatesOfJersey/e-petitions,ansonK/e-petitions,joelanman/e-petitions,oskarpearson/e-petitions,StatesOfJersey/e-petitions,StatesOfJersey/e-petitions,alphagov/e-petitions,oskarpearson/e-petitions,ansonK/e-petitions